1. Field of the Invention
The present invention relates to a waveguide structure, a manufacturing method thereof and a heat assisted magnetic recording head (HAMR) using the same, and more particularly to a waveguide structure, a manufacturing method thereof and a heat assisted magnetic recording head, wherein the improvement of beam intensity and the maintenance of a single focusing spot are attained even after an input beam passes through a nano-aperture.
2. Description of the Prior Art
As generally known in the art, the practice of magnetic recording in which only a magnetic field is utilized for recording data has a limitation in high-density recording due to thermal instability. As an alternative to overcome this shortcoming, a heat assisted magnetic recording head (HAMR) to which a light transmission module is applied has been disclosed, wherein the recording is accelerated by locally heating a magnetic recording medium with a light emission and temporarily reducing coercive force.
FIG. 1 schematically shows a conventional heat assisted magnetic recording (HAMR) head 10. The conventional HAMR head 10 comprises a magnetic recording unit 20 and a light transmission module 30 for heating a magnetic recording medium 40.
The magnetic recording unit 20 includes a recording pole 21 for applying the magnetic recording field to the magnetic recording medium 40 and a return pole 25 for being connected to the recording pole 21 through a yoke 23 and forming a magnetic path.
The light transmission module 30, which serves to heat the predetermined area A of the magnetic recording medium 40 through a near-field emission, includes a light source 31 and a waveguide 35 for guiding the light emitted from the light source 31. Here, the light source 31 is coupled to the waveguide 35 through an optic fiber 33 for transmitting the light and a stack-type spherical surface lens 34 for collimating the light emitted from the optic fiber 33.
Here, the magnetic recording medium 40 moves relatively to the HAMR head 10 in a direction indicated by an arrow D and the heated area A is located on the recording pole 21 by the relative movement of the magnetic recording medium 40. Thus, the recording pole 21 can perform a vertical magnetic recording on the heated area, so that the magnetic recording can be attained without thermal instability.
As described herein before, the conventional HAMR head 10 comprises such a structure that the waveguide 35 is attached to the outer side of the recording pole 21 in associating the magnetic recording unit 20 with the light transmission module 30. Accordingly, a certain distance can be maintained between the waveguide 35 and the magnetic recording medium 40 when the magnetic recording unit 20 buoys from the magnetic recording unit 20 by means of an air bearing.
On the other hand, in order to locally provide the HAMR head 10 with the heat source, the light (or the beam) should be delivered to a nano-aperture 37 located at an end of the waveguide 35 and the beam passing through the nano-aperture 37 can cause local application of the heat while effecting the field enhancement.
However, in the conventional HAMR head having the above-described structure, the beam passing through the nano-aperture 37 causes the order difference of two magnitudes to occur due to the small outline package (SOP) of the input beam. (L. Hasselink: Proc, SPIE, Vol. 4342. pp 325 (2002)).
Also, if a profile of the 3D waveguide is similar to a slab for the purpose of attaining a high polarization dependent loss (PDL) as in a cavity of a laser diode, coupling of the light source to the waveguide becomes difficult and thus an efficient system can not be obtained.
Further, due to the small outline package (SOP) of the input beam, differences may occur in intensity distribution of the beam spot formed after passing through the nano-aperture 37, and there may be two peaks when the polarization of the input beam is not appropriately controlled. (Jiying Xu: Opt. Engr. Vol. 44. pp 01800-1 (2005)).
Further, since the loss of the beam and the polarization in an undesirable direction occur when the beam is transmitted through the waveguide 35, there are the problems in that the beam intensity decreases and the shape of the beam changes after passing through the nano-aperture 37.